Phys 1240: Sound and MusicLAST: resonance, and percussioninstrumentsTODAY: string, and wind instrumentsNEXT: Exam. See web for detailsREAD: Nothing new for Thursday.For a week from now, 4.1, then 4.5(though, we won’t really discussrefraction much. We’ll come backto 4.2/4.3 NEXT).Study session - RamaleyRAMY C-250 Wed evening, 7-9!CT 3.3.1aWhich lasts longer, the vibration of astring on an electric guitar, or on anacoustic guitar?(Assume the same string, pluckedthe same)A) Electric guitar strings vibratelongerB) Acoustic guitar strings vibratelongerC) Both should vibrate the sameD) ???CT 3.3.2If I shorten the string of this instrument whathappens?a) The pitch goes upb) The pitch goes downc) The sound gets louderd) The sound gets quietere) More than one of theseWhat if I increase the tension?CT 3.4.3aHow do you raise the pitch of a stringinstrument by exactly one octave?a) Put your finger down exactly halfwayalong the stringb) Put your finger down somewhere elsec) Increase the tension by a factor of 2d) More than one of theseDoes this same idea work for percussion instruments (like a drum head?)Freq (SHM) = const * √ (K/mass) λ * freq = speed of wave = const* (√ Tension/mass)OctavesDoubling the frequency produces a tone which is“the same” (sort of!) => It’s one octave higherSame NAME (e.g. middle C, go up by a factor of 2in frequency, you’re back to C again)WHY?CONNECTION TO LENGTH? (metal bars: speed of transverse waves dependson wavelength!)StringsThings to think about:• Effect of tension (or stringmass, or string length)• Frets• Extra (resonating) strings (e.g.triple strings on piano)• Coupling vibrations to air (!!)• Plucking vs sustaining (bows)CT 3.4.3bHow do you raise the pitch of a wind instrumentby exactly one octave?a) Halve the effective length of the tubeb) Change the length, but not by 1/2 (!)c) Halve the diameter of the tubed) Blow half as harde) More than one of theseCT 3.4.1A long tube produces a soundIf I cut the tube in half, the pitch will be…compared to the originala) Higher by an octaveb) Higher, but not by an octavec) Lowerd) Lower, but not by an octavee) the same asWhat if I make the diameter of the tube larger?What if I blow harder?CT 3.4.2What is the function of finger holes in a flute?a) To create an edgetoneb) To shorten or lengthen the pipec) Emphasizes the affects of the reedd) Mostly aesthetice) More than one of theseCT 3.4.3If we halve the length of a tube in a windinstrument what will happen?a) The period is halvedb) The frequency is doubledc) Raises the pitch one octaved) Both a and be) a, b, and cCT 3.4.xf * λ = speedIf “f” refers to the vibrationalfrequency of the string, and λ isthe wavelength of the wave onthe string, what is the relevant“speed” for a string instrument?A) 344 m/sB) Something totally different!Same question, but referring to the Pressure vibrations inside a wind instrument?CT 3.4.4What is the function of the flared bell on the endof a recorder?a) It aids in projecting the musicb) It slows the speed of the sound beingproducedc) It lowers pitch of the noted) It is mostly for visual effecte) Some other important functionWinds• Edgetones (flute, recorder, organ) vs Reeds single (clarinet: cylindrical sax: conical) or double (oboe, bassoon)•Resonating chamberCylindrical vs conical• Woodwinds (all the above) vsBrass (mouthpiece/lips)• Voice (kind of like brass!)CT 3.5.1What is the key difference between a flute anda recorder?a) One of them has a reed and the other does notb) One makes use of an edgetone and the other doesnotc) One of them has a double reed and one has asingle reedd) Something elsee) More than one of the aboveWhat is the key difference between an oboeand a clarinet?CT 3.3.1bThe sound that you hear from a violinis produced by:a) Mostly stringsb) Mostly the wood in the backc) Both equallyd) None of the above“You can’t fan a fire with a knitting needle”CTR• What is sound? How do you describe itmicroscopically? How do you represent itgraphically?• How are frequency, wavelength, period,amplitude, speed, loudness, pitch,pressure,… Defined? Related? Whatdo they depend on? Why?• Simple harmonic motion, and the(metaphorical?) connections to sound• What experiments have we done todemonstrate/make sense of theseproperties and relations?CTR1.1This graph shows the height of asmall spot on the string as thetraveling wave moves along. What’sthe wavelength of this wave?3Time (sec)Amplitude.1 mA traveling wave moves along astring. A given “peak” moves alongthe full 5 m long string in 1 secA)10 m B) .67 m C) 2 mD) 0.1 m E) 2.5 mCTR1.2A singer holds a note, singing into amicrophone which is plugged into anoscilloscope. The trace is shown below.What is the frequency of the sung note?123Voltsm sec00.1A)1 HzB)2 HzC)500 HzD)1000 HzE)Something else/not sureCTR1.3You’re clapping in front of a wall, adistance “D” away from you. Thepattern isclap-pause-echo-pause-clap-pause-echo…(evenly spaced… picture it!)Your friend times your claps (not theechos!) and counts 6 claps in 10seconds.What’s the speed of sound?A) 4 D / (0.6 sec)B) 2 D / (0.6 sec)C) D / (0.6 sec)D) 10 D / (.6 sec)E) D / (1.2 sec)TR1.4A singer is singing into amicrophone which is plugged intoan oscilloscope. They are singingat a constant pitch (“concert A”)but getting steadily louder andlouder. What would the ‘scopetrace look like?What if they are singing at aSteady volume, but gettinghigher and higher in pitch?PhysletsPhyslet: periodic motionPhyslet: waves/superpositionPhyslet:
View Full Document
Unlocking...